The skull is hard and inflexible, while the brain is soft with the consistency of gelatin. The brain is encased inside the skull. The movement of the skull through space (acceleration) followed by the rapid discontinuation of this action when the skull meets a stationary object (deceleration) causes the brain to move inside the skull. The brain moves at a different rate than the skull, and different parts of the brain move at different speeds because of their relative lightness or heaviness. The differential movement of the skull and the brain when the head is struck results in direct brain injury, due to diffuse axonal shearing, contusion and brain swelling.
The helmet of the present invention relates to all types of helmets. One type of helmet is a military helmet, which is a helmet utilized by military personnel in combat. The military helmets currently in use have a Kevlar or projectile resistant shell that have a number of non-functionally-interconnected pads to hold the helmet in place. The pads are made from a visco-elastic, high-energy absorption foam. While it provides protection from a diverse range of extraneous insults to the head, it cannot prevent deceleration (i.e., diffuse axonal injury) or other types of projectile injuries (e.g., bullet that perforates the helmet).
Under healthy conditions, the average or mean brain temperature (about 38° C.) exceeds body-core temperature (about 37.5° C.) by about 0.2° C. to about 0.5° C. The “core temperature” refers to the temperature of the deep tissues of the body. This temperature is maintained with minimal fluctuations by a range of autonomic/endocrinological adjustments, which are effective under normal conditions. The temperature control may fail under pathological conditions, including fever and hyperthermia, which are defined herein as different entities.
Fever is part of the body's defense mechanism against viruses or bacteria, where the hypothalamus, which behaves like a thermostat and is the primary organ that regulates temperature in the body, loses its ability to properly sense the temperature. This allows shivering to occur, which generates extra heat, in order to stimulate the efficacy of the immune system. Having a temperature increase, in the absence of brain or spinal cord injury, helps the body fight infection-mediated illness.
In contrast, hyperthermia is an elevated body temperature that occurs independently of body infection and may become a medical emergency requiring immediate treatment to prevent disability or death. The most common causes are heat stroke, adverse reactions to drugs and malignant hyperthermia (following anesthesia by halothane). Focal and regional, as opposed to systemic, increases in brain temperature are also observed following traumatic brain injury and stroke.
The opposite of hyperthermia is hypothermia, which occurs when an organism's core temperature drops below 36° C. or the temperature required for normal body functions. Hypothermia can be induced systemically or focally by exposure to cooling agents.
Brain temperature exceeds body-core temperature by 0.2° C.-0.5° C. (“core temperature” may be extrapolated from the bladder or rectal temperature). Maintaining a constant core temperature, or preventing an increase in temperature, following a variety of brain insults, is not enough to antagonize the development of long-term lesions. At present, the neuroprotective properties of mild hypothermia (defined here as reflecting a brain temperature between 33° C. and 36° C.) have been demonstrated in numerous studies. Mild hypothermia is one of the most effective neuroprotective therapies against brain ischemia and trauma that currently exists. Preliminary clinical studies have shown that mild hypothermia can be a relatively safe treatment. The feasibility of using mild hypothermia to treat stroke and spinal cord injury patients has been evaluated in various clinical trials. Increasing emphasis is being placed on developing techniques and protocols to ensure rapid cooling of patients. One of the greatest obstacles in moving the application of brain cooling hypothermia from the hospital setting to the field (e.g. war/civilian) has been the availability of adequate cooling techniques.
Generalized hypothermia was initially achieved by surface cooling, which sometimes meant submerging the neurosurgical patient in iced water while the patient was on the operating table. This method of cooling was unwieldy and required prolonged anesthesia. More recently, the feasibility of active core cooling to 32° C. using an extracorporeal heat exchanger was performed in patients with severe head injuries. At the present time, systemic surface cooling is a widely used method to induce brain systemic hypothermia using water-circulating blankets.
As cooling devices and methods are improved and proven to be effective, more data concerning the effect of temperature reduction on injury and illness recovery should be forthcoming.
To prevent shivering after heat reduction, the hypothermia-treated patient should be sedated. Both clinicians and basic scientists remain optimistic that over this decade hypothermia will emerge as a major effective therapeutic advance for patients with acute neurologic injury. However, an effective, simple hypothermic apparatus for field use remains to be developed. For example U.S. Pat. Nos. 6,969,399; 7,056,334; 7,077,858; 7,087,075; 7,179,279; 7,303,579; 6,986,783; 7,056,282 and U.S. Patent Pub. No. 2010/0211140 all disclose cooling techniques and systems; however, none of these systems are suitable for use in non-hospital settings. Moreover, for mild hypothermia to be effective, studies have shown that it must be induced within four hours of injury. See Clifton et al., Lack of effect of induction of hypothermia after acute brain injury, New England Journal of Medicine 2001 Feb. 22; 344(8):556-63; Clifton, Is keeping cool still hot? An update on hypothermia in brain injury, Current Opinion in Critical Care, 10(2):116-9 (April 2004).
Therefore, a need exists for developing an effective, simple hypothermic apparatus for mobile use such as in a field setting. The helmet can used by soldiers in war or by civilians. The helmet use will selectively and uniformly lower a user's brain temperature slowly in a controlled manner so as to avoid the risks associated with rapid induction of hypothermia. It would be highly desirable to provide an effective, controlled mechanism, that can be triggered by third parties immediately following brain injury, that has the effect of preventing the increase in intracranial pressure, swelling and acute and long-term damage. To effectively achieve these goals, the apparatus would need to be effective without removing the patients existing clothing, including war/civilian helmets. For example U.S. Pat. Nos. 4,552,149; 4,753,242; 5,261,399; 5,539,934; 5,871,526; 5,913,885; 5,957,964; 6,030,412; 6,126,680; 6,183,501; 6,277,143; 6,312,453; 6,416,532; 6,461,379; 6,682,552; 6,962,600 and 7,846,118 disclose hats, wraps, covers, etc. for cooling body temperatures; however, all of these systems would require removing the patient's current helmet or clothing in the field, which could exacerbate the patient's condition or, in the case of combat use, leave the patient vulnerable to further attack. In addition, the system would need to be highly mobile and be incorporated into the user's current equipment, meaning that the system or apparatus would not obstruct the user, impair the functioning of the user's current equipment, or be susceptible to failure resulting from incidental damage prior to activation as could occur in other such systems. See U.S. Pat. Nos. 4,691,762; 7,008,445; 7,052,509; 7,507,250; 7,565,705 and 7,621,945.